Lithographic apparatus and a device manufacturing method

ABSTRACT

A lithographic apparatus having: a substrate table constructed to hold a substrate; a projection system configured to project a patterned radiation beam onto a target portion of the substrate; a substrate surface actuator including a fluid opening for fluid flow therethrough from/onto a facing surface facing the substrate surface actuator to generate a force between the substrate surface actuator and the facing surface, the facing surface being a top surface of the substrate or a surface substantially co-planar with the substrate; and a position controller to control the position and/or orientation of a part of the facing surface by varying fluid flow through the fluid opening to displace the part of the facing surface relative to the projection system.

This application is a continuation of U.S. patent application Ser. No.13/693,923, filed on Dec. 4, 2012, which claims priority and benefitunder 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No.61/567,988, filed on Dec. 7, 2011. The content of each of thoseapplications is incorporated herein in its entirety by reference.

FIELD

The present invention relates to a lithographic apparatus and a methodfor manufacturing a device using a lithographic apparatus.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In that instance, a patterning device, whichis alternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern to be formed on an individual layer of theIC. This pattern can be transferred onto a target portion (e.g.comprising part of, one, or several dies) on a substrate (e.g. a siliconwafer). Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion at one time, andso-called scanners, in which each target portion is irradiated byscanning the pattern through a radiation beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

It has been proposed to immerse the substrate in the lithographicprojection apparatus in a liquid having a relatively high refractiveindex, e.g. water, so as to fill a space between the final element ofthe projection system and the substrate. In an embodiment, the liquid isdistilled water, although another liquid can be used. An embodiment ofthe invention will be described with reference to liquid. However,another fluid may be suitable, particularly a wetting fluid, anincompressible fluid and/or a fluid with higher refractive index thanair, desirably a higher refractive index than water. Fluids excludinggases are particularly desirable. The point of this is to enable imagingof smaller features since the exposure radiation will have a shorterwavelength in the liquid. (The effect of the liquid may also be regardedas increasing the effective numerical aperture (NA) of the system andalso increasing the depth of focus.) Other immersion liquids have beenproposed, including water with solid particles (e.g. quartz) suspendedtherein, or a liquid with a nano-particle suspension (e.g. particleswith a maximum dimension of up to 10 nm). The suspended particles may ormay not have a similar or the same refractive index as the liquid inwhich they are suspended. Other liquids which may be suitable include ahydrocarbon, such as an aromatic, a fluorohydrocarbon, and/or an aqueoussolution.

Submersing the substrate or substrate and substrate table in a bath ofliquid (see, for example, U.S. Pat. No. 4,509,852) means that there is alarge body of liquid that must be accelerated during a scanningexposure. This requires additional or more powerful motors andturbulence in the liquid may lead to undesirable and unpredictableeffects.

In an immersion apparatus, immersion fluid is handled by a fluidhandling system, device structure or apparatus. In an embodiment thefluid handling system may supply immersion fluid and therefore be afluid supply system. In an embodiment the fluid handling system may atleast partly confine immersion fluid and thereby be a fluid confinementsystem. In an embodiment the fluid handling system may provide a barrierto immersion fluid and thereby be a barrier member, such as a fluidconfinement structure. In an embodiment the fluid handling system maycreate or use a flow of gas, for example to help in controlling the flowand/or the position of the immersion fluid. The flow of gas may form aseal to confine the immersion fluid so the fluid handling structure maybe referred to as a seal member; such a seal member may be a fluidconfinement structure. In an embodiment, immersion liquid is used as theimmersion fluid. In that case the fluid handling system may be a liquidhandling system. In reference to the aforementioned description,reference in this paragraph to a feature defined with respect to fluidmay be understood to include a feature defined with respect to liquid.

SUMMARY

In a lithographic apparatus, there exists a difficulty that apositioning actuator to position the substrate may apply a force to thesubstrate some distance from a target portion of the substrate which iscurrently being illuminated. This can result in difficulty inpositioning the target portion of the substrate accurately. Thedifficulty can arise, for example, due to a variation in force beingapplied to the substrate (for example from a fluid handling system) ordue to the stiffness of a substrate support allowing some bending of thesubstrate.

It is desirable, for example, to be able to accurately position a targetportion of a substrate in a lithographic apparatus.

According to an aspect, there is provided a lithographic apparatuscomprising: a substrate table constructed to hold a substrate; aprojection system configured to project a patterned radiation beam ontoa target portion of the substrate; a substrate surface actuatorcomprising at least one fluid opening for fluid flow therethroughfrom/onto a facing surface facing the substrate surface actuator togenerate a force between the substrate surface actuator and the facingsurface, the facing surface being a top surface of the substrate or asurface substantially co-planar with the substrate; and a positioncontroller to control the position and/or orientation of a part of thefacing surface by varying fluid flow through the fluid opening todisplace the part of the facing surface relative to the projectionsystem.

According to an aspect, there is provided a device manufacturing methodcomprising: using a projection system to project a patterned radiationbeam onto a target portion of a substrate; and using a substrate surfaceactuator to control a position and/or orientation of a facing surfacefacing the substrate surface actuator relative to the projection systemby varying fluid flow from/onto the facing surface through at least onefluid opening of a substrate surface actuator, the facing surface beinga top surface of the substrate or a surface substantially co-planar withthe substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIGS. 2 and 3 depict a liquid supply system for use in a lithographicprojection apparatus;

FIG. 4 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 5 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 6 depicts, in plan, a substrate surface actuator of an embodiment;

FIG. 7 depicts, in cross-section, one way in which the force between asubstrate surface actuator and the substrate may be varied;

FIG. 8 illustrates, in cross-section, how a substrate surface actuatormay be mounted;

FIG. 9 illustrates, in cross-section, a discrete fluid opening;

FIG. 10 depicts, in plan, a substrate surface actuator of an embodiment;

FIG. 11 depicts, in cross-section, a substrate surface actuator of anembodiment;

FIG. 12 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment;

FIG. 13 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment;

FIG. 14 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment;

FIG. 15 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment;

FIG. 16 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment;

FIG. 17 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment;

FIG. 18 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment;

FIG. 19 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment;

FIG. 20 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment;

FIG. 21 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment;

FIG. 22 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment; and

FIG. 23 illustrates, schematically and in plan, a substrate surfaceactuator of an embodiment.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus comprises:

-   -   an illumination system (illuminator) IL configured to condition        a radiation beam B (e.g. UV radiation or DUV radiation);    -   a support structure (e.g. a mask table) MT constructed to        support a patterning device (e.g. a mask) MA and connected to a        first positioner PM configured to accurately position the        patterning device MA in accordance with certain parameters;    -   a support table, e.g. a sensor table to support one or more        sensors or a substrate table WT constructed to hold a substrate        (e.g. a resist-coated substrate) W, connected to a second        positioner PW configured to accurately position the surface of        the table, for example of a substrate W, in accordance with        certain parameters; and    -   a projection system (e.g. a refractive projection lens system)        PS configured to project a pattern imparted to the radiation        beam B by patterning device MA onto a target portion C (e.g.        comprising one or more dies) of the substrate W.

The illumination system IL may include various types of opticalcomponents, such as refractive, reflective, magnetic, electromagnetic,electrostatic or other types of optical components, or any combinationthereof, for directing, shaping, or controlling radiation.

The support structure MT holds the patterning device MA. It holds thepatterning device MA in a manner that depends on the orientation of thepatterning device MA, the design of the lithographic apparatus, andother conditions, such as for example whether or not the patterningdevice MA is held in a vacuum environment. The support structure MT canuse mechanical, vacuum, electrostatic or other clamping techniques tohold the patterning device MA. The support structure MT may be a frameor a table, for example, which may be fixed or movable as required. Thesupport structure MT may ensure that the patterning device MA is at adesired position, for example with respect to the projection system PS.Any use of the terms “reticle” or “mask” herein may be consideredsynonymous with the more general term “patterning device.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device MA may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two or more tables(or stages or supports), e.g., two or more substrate tables or acombination of one or more substrate tables and one or more sensor ormeasurement tables. In such “multiple stage” machines the multipletables may be used in parallel, or preparatory steps may be carried outon one or more tables while one or more other tables are being used forexposure. The lithographic apparatus may have two or more patterningdevice tables (or stages or supports) which may be used in parallel in asimilar manner to substrate, sensor and measurement tables.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source SO and the lithographic apparatus may beseparate entities, for example when the source SO is an excimer laser.In such cases, the source SO is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDcomprising, for example, suitable directing mirrors and/or a beamexpander. In other cases the source SO may be an integral part of thelithographic apparatus, for example when the source SO is a mercurylamp. The source SO and the illuminator IL, together with the beamdelivery system BD if required, may be referred to as a radiationsystem.

The illuminator IL may comprise an adjuster AD for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator IL can be adjusted. In addition, the illuminator IL maycomprise various other components such as an integrator IN and acondenser CO. The illuminator IL may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross-section. Similar to the source SO, the illuminator IL may or maynot be considered to form part of the lithographic apparatus. Forexample, the illuminator IL may be an integral part of the lithographicapparatus or may be a separate entity from the lithographic apparatus.In the latter case, the lithographic apparatus may be configured toallow the illuminator IL to be mounted thereon. Optionally, theilluminator IL is detachable and may be separately provided (forexample, by the lithographic apparatus manufacturer or anothersupplier).

The radiation beam B is incident on the patterning device (e.g., mask)MA, which is held on the support structure (e.g., mask table) MT, and ispatterned by the patterning device MA. Having traversed the patterningdevice MA, the radiation beam B passes through the projection system PS,which focuses the beam onto a target portion C of the substrate W. Withthe aid of the second positioner PW and position sensor IF (e.g. aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g. so as to positiondifferent target portions C in the path of the radiation beam B.Similarly, the first positioner PM and another position sensor (which isnot explicitly depicted in FIG. 1) can be used to accurately positionthe patterning device MA with respect to the path of the radiation beamB, e.g. after mechanical retrieval from a mask library, or during ascan. In general, movement of the support structure MT may be realizedwith the aid of a long-stroke module (coarse positioning) and ashort-stroke module (fine positioning), which form part of the firstpositioner PM. Similarly, movement of the substrate table WT may berealized using a long-stroke module and a short-stroke module, whichform part of the second positioner PW. In the case of a stepper (asopposed to a scanner) the support structure MT may be connected to ashort-stroke actuator only, or may be fixed. Patterning device MA andsubstrate W may be aligned using patterning device alignment marks M1,M2 and substrate alignment marks P1, P2. Although the substratealignment marks as illustrated occupy dedicated target portions, theymay be located in spaces between target portions C (these are known asscribe-lane alignment marks). Similarly, in situations in which morethan one die is provided on the patterning device MA, the patterningdevice alignment marks may be located between the dies.

The depicted apparatus could be used in at least one of the followingmodes:

1. In step mode, the support structure MT and the substrate table WT arekept essentially stationary, while an entire pattern imparted to theradiation beam B is projected onto a target portion C at one time (i.e.a single static exposure). The substrate table WT is then shifted in theX and/or Y direction so that a different target portion C can beexposed. In step mode, the maximum size of the exposure field limits thesize of the target portion C imaged in a single static exposure.

2. In scan mode, the support structure MT and the substrate table WT arescanned synchronously while a pattern imparted to the radiation beam Bis projected onto a target portion C (i.e. a single dynamic exposure).The velocity and direction of the substrate table WT relative to thesupport structure MT may be determined by the (de-)magnification andimage reversal characteristics of the projection system PS. In scanmode, the maximum size of the exposure field limits the width (in thenon-scanning direction) of the target portion C in a single dynamicexposure, whereas the length of the scanning motion (and size of theexposure field) determines the height (in the scanning direction) of thetarget portion C.

3. In another mode, the support structure MT is kept essentiallystationary holding a programmable patterning device, and the substratetable WT is moved or scanned while a pattern imparted to the radiationbeam is projected onto a target portion C. In this mode, generally apulsed radiation source is employed and the programmable patterningdevice is updated as required after each movement of the substrate tableWT or in between successive radiation pulses during a scan. This mode ofoperation can be readily applied to maskless lithography that utilizesprogrammable patterning device, such as a programmable mirror array of atype as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications in manufacturing components with microscale, or evennanoscale, features, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc.

In a lithographic apparatus the position of a substrate is changed usingthe second positioner PW. The second positioner PW changes the positionof a substrate support on which the substrate W sits. There can be somedistance between the actuators of the second positioner PW and part ofthe substrate W where the substrate W is being illuminated (e.g. at atarget portion C). Additionally the substrate support may not beperfectly stiff so that it becomes difficult, if not impossible, toaccurately position the substrate W based only on signals sent to thesecond positioner PW.

With an increase in the substrate area, unless a substrate table WT andsubstrate stage is made thinner, the depth of the substrate table WT isincreased in the same proportion as the width and the length of thesubstrate table WT, and thus the width (e.g., diameter) of thesubstrate. Thus, although, for example, for a 450 mm substrate Wrelative to a 300 mm substrate, the diameter increases proportionatelyby 50%, the area of the substrate W and substrate table WT eachincreases by 125% and the volume and mass of the substrate table WTwould increase by almost 240%. Such an increase in volume isundesirable. However, in having a thinner substrate table WT, the tableis less stiff, more flexible and susceptible to bending. Consequently,accurate positioning of the substrate table WT and the substrate W it issupporting is more difficult. A measure should be provided to enablesuch a more flexible substrate table WT to be used effectively, i.e. itsposition to be sufficiently accurately known.

It would be desirable, for example, to position and/or orientate thesubstrate W by applying a force at a position closer to the targetportion C of the substrate W. For example, positioning the substrate byapplying a force directly to the substrate W within a distance of lessthan 10 target portion C widths (e.g. the dimension of a target portionin a direction orthogonal to the scanning direction and in the plane ofthe top surface of the substrate W) would be beneficial. This is becausethe closer the force can be applied to the portion of the substrate Wcurrently being imaged (i.e. the part which is most important) the moreaccurately positioned that part of the substrate can be. In anembodiment the force is applied at least one target portion C width fromthe optical axis, desirably at least two. This is because the furtherfrom the optical axis the force is applied, the lower the force needs tobe to move the substrate W.

In an embodiment of the present invention, a substrate surface actuator100 such as illustrated in FIGS. 1 and 6 is provided. The substratesurface actuator 100 generates a force between the substrate surface(the top surface) and the substrate surface actuator 100. An embodimentis described below with reference to the force being applied to thesubstrate W, but the invention is not limited to this. The substratesurface actuator 100 is an actuator which applies a force of a surfacewhich is substantially in the plane of a substrate W when mounted on asubstrate supportable WT. This includes the surface of the substratetable WT around the substrate W and any other table such as anothersubstrate table WT, a measurement table and/or a table used forsubstrate W swap. Reference to a top surface of a substrate W includesany surface which is substantially co-planar with such a top surface ofa substrate or moves beneath the projection system PS and so ‘faces’ theprojection system PS, i.e. is a facing surface. The substrate surfaceactuator 100 can be used to control the position and/or orientation of aportion of the facing surface.

In an embodiment the force is applied in a non-physical contact manner,for example with a fluid. For this purpose, the substrate surfaceactuator 100 has at least one fluid opening for fluid flow therethroughfrom and/or onto a top surface of the substrate W. The flow therethroughgenerates the force between the substrate surface actuator 100 and thesubstrate W.

A position controller 500 is configured to control the position of thesubstrate W by varying fluid flow through the fluid opening of thesubstrate surface actuator 100. Varying fluid flow through the fluidopening displaces the substrate W (because of the change in forceapplied to the substrate W). This can be used to change the position ofthe substrate W relative to the projection system PS. The positioncontroller 500 may be the same position controller or a differentposition controller to the one which controls the second positioner PW.

In an immersion lithographic apparatus, liquid is provided between afinal element of a projection system PS and the substrate W. A fluidhandling system 12 confines liquid to a space between a final element ofthe projection system PS and the substrate W. Such a fluid handlingstructure 12 often applies a force between the fluid handling system 12and the substrate W. The force applied can vary (in particular if thereis two phase extraction of fluid between the fluid handling structure 12and the substrate W). Such variation in force can lead to displacementof the target portion C of the substrate W relative to the projectionsystem PS and thereby imaging errors.

The provision of a fluid handling structure 12 in an immersionlithographic apparatus is convenient for the case where a substratesurface actuator 100 is provided. This is because the fluid opening ofthe substrate surface actuator 100 can be a pre-existing opening in thefluid handling structure 12 which handles immersion fluid and/or otherfluid to control the position and/or supply of immersion fluid.Alternatively or additionally, the fluid opening of the substratesurface actuator 100 can be a separate opening in the fluid handlingstructure 12 which has no purpose other than to provide the forcerequired of the substrate surface actuator 100.

For simplicity some embodiments will be described in which the fluidopening of the substrate surface actuator 100 is provided in a fluidhandling structure 12 of an immersion lithographic apparatus. However,an embodiment of the invention can be applied to a non-immersionlithographic apparatus, for example as will be described with referenceto FIGS. 8 and 9 below.

Arrangements for providing liquid between a final element of theprojection system PS and the substrate can be classed into three generalcategories. These are the bath type arrangement, the so-called localizedimmersion system and the all-wet immersion system. In a bath typearrangement substantially the whole of the substrate W and optionallypart of the substrate table WT is submersed in a bath of liquid.

A localized immersion system uses a liquid supply system in which liquidis only provided to a localized area of the substrate. One way which hasbeen proposed to arrange for this is disclosed in PCT patent applicationpublication no. WO 99/49504. The space filled by liquid is smaller inplan than the top surface of the substrate and the area filled withliquid remains substantially stationary relative to the projectionsystem PS while the substrate W moves underneath that area. FIGS. 2-6,10 and 11 show different supply devices which can be used in such asystem. A sealing feature is present to seal liquid to the localizedarea.

In an all wet arrangement the liquid is unconfined. The whole topsurface of the substrate and all or part of the substrate table iscovered in immersion liquid. The depth of the liquid covering at leastthe substrate is small. The liquid may be a film, such as a thin film,of liquid on the substrate. Immersion liquid may be supplied to or inthe region of a projection system and the facing surface facing. Any ofthe liquid supply devices of FIGS. 2-6, 10 and 11 can also be used insuch a system. However, a sealing feature is not present, not activated,not as efficient as normal or otherwise ineffective to seal liquid toonly the localized area.

As illustrated in FIGS. 2 and 3, liquid is supplied by at least oneinlet onto the substrate, desirably along the direction of movement ofthe substrate relative to the final element. Liquid is removed by atleast one outlet after having passed under the projection system. As thesubstrate is scanned beneath the element in a −X direction, liquid issupplied at the +X side of the element and taken up at the −X side. FIG.2 shows the arrangement schematically in which liquid is supplied via aninlet and is taken up on the other side of the element by an outletwhich is connected to a low pressure source. In the illustration of FIG.2 the liquid is supplied along the direction of movement of thesubstrate relative to the final element, though this does not need to bethe case. Various orientations and numbers of in-and outlets positionedaround the final element are possible; one example is illustrated inFIG. 3 in which four sets of an inlet with an outlet on either side areprovided in a regular pattern around the final element. Note that thedirection of flow of the liquid is shown by arrows in FIGS. 2 and 3.

A further immersion lithography solution with a localized liquid supplysystem is shown in FIG. 4. Liquid is supplied by two groove inlets oneither side of the projection system PS and is removed by a plurality ofdiscrete outlets arranged radially outwardly of the inlets. The inletscan be arranged in a plate with a hole in its centre and through whichthe projection beam is projected. Liquid is supplied by one groove inleton one side of the projection system PS and removed by a plurality ofdiscrete outlets on the other side of the projection system PS, causinga flow of a thin film of liquid between the projection system PS and thesubstrate W. The choice of which combination of inlet and outlets to usecan depend on the direction of movement of the substrate W (the othercombination of inlet and outlets being inactive). Note that thedirection of flow of fluid and of the substrate is shown by arrows inFIG. 4.

Another arrangement which has been proposed is to provide the liquidsupply system with a liquid confinement structure which extends along atleast a part of a boundary of the space between the final element of theprojection system and the substrate, substrate table or both. Such anarrangement is illustrated in FIG. 5.

FIG. 5 schematically depicts a localized liquid supply system or fluidhandling structure 12. The fluid handing structure serves as a barrier,confining liquid to a localized surface of the underneath surface, suchas of a substrate W, a substrate table WT or both. The fluid handlingstructure extends along at least a part of a boundary of the spacebetween the final element of the projection system and the substratetable WT or substrate W. (Please note that reference in the followingtext to surface of the substrate W also refers in addition or in thealternative to a surface of the substrate table, unless expressly statedotherwise.) The fluid handling structure 12 is substantially stationaryrelative to the projection system in the XY plane though there may besome relative movement in the Z direction (in the direction of theoptical axis). In an embodiment, a seal is formed between the fluidhandling structure 12 and the surface of the substrate W. The seal maybe a contactless seal such as a gas seal (such a system with a gas sealis disclosed in European patent application publication no.EP-A-1,420,298) or liquid seal.

The fluid handling structure 12 at least partly contains liquid in thespace 11 between a final element of the projection system PS and thesubstrate W. A contactless seal 16 to the substrate W may be formedaround the image field of the projection system PS so that liquid isconfined within the space between the substrate W surface and the finalelement of the projection system PS. The space 11 is at least partlyformed by the fluid handling structure 12 positioned below andsurrounding the final element of the projection system PS. Liquid isbrought into the space below the projection system PS and within thefluid handling structure 12 by liquid inlet 13. The liquid may beremoved by liquid outlet 13. The fluid handling structure 12 may extenda little above the final element of the projection system. The liquidlevel rises above the final element so that a buffer of liquid isprovided. In an embodiment, the fluid handling structure 12 has an innerperiphery that at the upper end closely conforms to the shape of theprojection system or the final element thereof and may, e.g., be round.At the bottom, the inner periphery closely conforms to the shape of theimage field, e.g., rectangular, though this need not be the case.

The liquid may be contained in the space 11 by a gas seal 16 which,during use, is formed between the bottom of the fluid handling structure12 and the surface of the substrate W. The gas seal is formed by gas.The gas in the gas seal is provided underpressure via inlet 15 to thegap between the fluid handling structure 12 and substrate W. The gas isextracted via outlet 14. The overpressure on the gas inlet 15, vacuumlevel on the outlet 14 and geometry of the gap are arranged so thatthere is a high-velocity gas flow 16 inwardly that confines the liquid.The force of the gas on the liquid between the fluid handling structure12 and the substrate W contains the liquid in a space 11. Theinlets/outlets may be annular grooves which surround the space 11. Theannular grooves may be continuous or discontinuous. The flow of gas 16is effective to contain the liquid in the space 11. Such a system isdisclosed in United States patent application publication no. US2004-0207824, which is hereby incorporated by reference in its entirety.In an embodiment, the fluid handling structure 12 does not have a gasseal.

Another localized area arrangement is a fluid handling structure whichmakes use of a gas drag principle. The so-called gas drag principle hasbeen described, for example, in United States patent applicationpublication nos. US 2008-0212046, US 2009-0279060 and US 2009-0279062.In that system the extraction holes are arranged in a shape which maydesirably have a corner. The cornered shape has at least one low radiuspart (i.e. at a corner) which has a first radius of curvature which islow relative to a second radius of curvature at a high radius part (i.e.a part between corners and/or distant from corners). The low radius parthas a first radius of curvature which is lower than a second radius ofcurvature present at the high radius part. The second radius ofcurvature may be infinity i.e. the high radius part may be straight. Thecorner may be aligned with a preferred direction of movement, such asthe stepping or the scanning direction. This reduces the force on themeniscus between two openings in the surface of the fluid handingstructure for a given speed in the preferred direction compared to ifthe two outlets were aligned perpendicular to the preferred direction.However, an embodiment of the invention may be applied to a fluidhandling system which in plan has any shape, or has a component such asthe extraction openings arranged in any shape. Such a shape in anon-limiting list may include an ellipse such as a circle, a rectilinearshape such as a rectangle, e.g. a square, or a parallelogram such as arhombus or a cornered shape with more than four corners such as a fouror more pointed star.

In a variation of the system of US 2008/0212046 A1, to which anembodiment of the present invention may relate, the geometry of thecornered shape in which the openings are arranged allows sharp corners(between about 60° and 90°, desirably between 75° and 90° and mostdesirably between 75° and 85°) to be present for the corners alignedboth in the scan and in the stepping directions. This allows increasedspeed in the direction of each aligned corner. This is because thecreation of liquid droplets due to an unstable meniscus, for example inexceeding a critical speed, in the scanning direction is reduced. Wherecorners are aligned with both the scanning and stepping directions,increased speed may be achieved in those directions. Desirably the speedof movement in the scanning and stepping directions may be substantiallyequal.

FIG. 6 illustrates schematically and in plan a meniscus pinning featureof a fluid handling system or of a fluid handling structure 12 having anextractor embodying the gas drag principle and to which an embodiment ofthe present invention may relate. The meniscus pinning feature isdesigned to resist, desirably prevent (as much as possible) the passageof fluid radially outwardly from the space 11. The features of ameniscus pinning device illustrated in FIG. 6 may, for example, replacethe meniscus pinning arrangement 14, 15, 16 of FIG. 5. The meniscuspinning device of FIG. 6 is a form of extractor. The meniscus pinningdevice comprises a plurality of discrete openings 50. Each opening 50 isillustrated as being circular, though this is not necessarily the case.Indeed one or more of the openings 50 may be one or more selected from:circular, elliptical, rectilinear (e.g. square, or rectangular),triangular, etc. and one or more openings may be elongate. Each openinghas, in plan, a length dimension (i.e. in the direction from one openingto the adjacent opening) of greater than or equal to 0.2 mm, greaterthan or equal to 0.5 mm, or greater than or equal to 1 mm. In anembodiment, the length dimension is selected from the range of 0.1 mm to10 mm or selected from the range of 0.25 mm to 2 mm. In an embodiment,the width of each opening is selected from the range of 0.1 mm to 2 mm.In an embodiment the width of each opening is selected from the range of0.2 mm to 1 mm. In an embodiment the length dimension is selected fromthe range of 0.2 mm to 0.5 mm or selected from the range of 0.2 mm to0.3 mm. Inlet openings like those of FIG. 6 (labeled 180) may beprovided radially inwardly of the openings 50.

Each of the openings 50 of the meniscus pinning device of FIG. 6 may beconnected to a separate underpressure source. Alternatively oradditionally, all or a plurality of the openings 50 may be connected toa common chamber or manifold (which may be annular) which is itself heldat an underpressure. In this way a uniform underpressure at each or aplurality of the openings 50 may be achieved. The openings 50 can beconnected to a vacuum source and/or the atmosphere surrounding the fluidhandling system (or confinement structure) may be increased in pressureto generate the desired pressure difference.

In the embodiment of FIG. 6 the openings 50 are fluid extractionopenings. Each opening is an inlet for the passage of gas, liquid or atwo phase fluid of gas and liquid, into the fluid handling system. Eachinlet may be considered to be an outlet from the space 11.

The openings 50 are formed in a surface of a fluid handling structure12. The surface faces the substrate W and/or substrate table WT, in use.In an embodiment the openings 50 are in a substantially flat surface ofthe fluid handling structure 12. At least one of the openings may be ina ridge. The openings 50 may be defined by needles or tubes. The bodiesof some of the needles, e.g., adjacent needles, may be joined together.The needles may be joined together to form a single body. The singlebody may form the cornered shape as described above.

The openings 50 are the end of a tube or elongate passageway, forexample. Desirably the openings are positioned such that in use they aredirected to, desirably facing, the facing surface, e.g. the substrate W.The rims (i.e. outlets out of a surface) of the openings 50 may besubstantially parallel to a top surface of a part of the facing surface.An elongate axis of the passageway to which the opening 50 is connectedmay be substantially perpendicular (within ±45°, desirably within 35°,25° or even 15° from perpendicular) to the top of the facing surface,e.g., the top surface of the substrate W.

Each opening 50 is designed to extract a mixture of liquid and gas. Theliquid is extracted from the space 11 whereas the gas is extracted fromthe atmosphere on the other side of the openings 50 to the liquid. Thiscreates a gas flow as illustrated by arrows 100 and this gas flow iseffective to hold, e.g. pin, the meniscus 320 between the openings 50substantially in place as illustrated in FIG. 6. The gas flow helpsmaintain the liquid confined by momentum blocking, by a gas flow inducedpressure gradient and/or by drag (shear) of the gas (e.g., air) flow onthe liquid.

The openings 50 surround the space to which the fluid handling structuresupplies liquid. The openings 50 may be distributed in an undersurfaceof the fluid handling structure. The openings 50 may be substantiallycontinuously spaced around the space (although the spacing betweenadjacent openings 50 may vary). In an embodiment, liquid is extractedall the way around the cornered shape and is extracted substantially atthe point at which it impinges on the cornered shape. This is achievedbecause the openings 50 are formed all the way around the space (in thecornered shape). In this way the liquid may be confined to the space 11.The meniscus may be pinned by the openings 50, during operation.

In an embodiment a gas knife 210 in the form of a slit opening may beprovided around the meniscus pinning feature (e.g. the extractor 70 ofthe FIG. 11 embodiment described below or the openings 50 of the FIG. 6embodiment). A gas knife in the form of a slit opening might typicallyhave a width of 50 μm. The invention is not limited to a slit form ofopening surrounding the meniscus pinning feature and, as describedbelow, the slit opening may instead be a plurality of discreteapertures. Use of discrete gas supply openings compared to a slit may beadvantageous as described in U.S. patent application No. 61/506,442,filed on 11 Jul. 2011, which is hereby incorporated by reference in itsentirety.

Radially inwardly of the openings 50 which act as a meniscus pinningfeature are a plurality of immersion fluid supply openings 180 a-c.These provide immersion liquid between the fluid handling structure 12and the substrate W to help ensure that the narrow gap between theundersurface of the fluid handling structure 12 and the substrate W isfilled with liquid. The immersion fluid supply openings 180 a-c can beuseful in filling a gap between an edge of a substrate W and thesubstrate table WT with immersion liquid. This can eliminate or at leastreduce the chance of a bubble of gas finding its way from the gapbetween the substrate W and substrate table WT into the immersion space11.

Other geometries of the bottom of the fluid handling structure 12 arepossible. For example, any of the structures disclosed in U.S. patentapplication publication no. US 2004-0207824 or U.S. patent applicationpublication no. US 2010-0313974 could be used in an embodiment of thepresent invention.

In an embodiment the immersion fluid supply openings 180 a-c may act asthe at least one fluid opening of the substrate surface actuator 100.That is, the function of the plurality of immersion fluid supplyopenings 180 a-c is dual. First, they function to provide immersionliquid between the fluid handling structure 12 and the substrate W. Thisis to help ensure that the narrow gap between the undersurface of thefluid handling structure 12 and the substrate W is filled with liquid.Second, the plurality of immersion fluid supply openings 180 a-cfunction as the fluid opening of the substrate surface actuator 100. Byvarying the flow of fluid through the fluid openings 180 a-c a forcebetween the substrate surface actuator 100 and the substrate W can bevaried.

The rate of flow of fluid through the at least one fluid opening 180 a-cis controlled by the position controller 500. By varying the fluid flowthrough the fluid opening the position controller 500 can displace thesubstrate W relative to the projection system PS. In this way a forcecan be applied to the substrate relatively close to the target portionTP as illustrated in FIG. 6. Thus, the position of the target portion TPon a part of the substrate can be accurately controlled.

As can be seen, in the embodiment of FIG. 6 the fluid openings 180 a-cof the substrate surface actuator 100 are close to the target portionTP, and certainly within fewer than 10 target portion widths (the widthin the direction orthogonal to the scanning direction (direction X asillustrated in FIG. 6)). The closer the fluid openings 180 a-c of thesubstrate surface actuator 100 are to the target portion TP the betterfor accuracy. In an embodiment the fluid openings are closer than fivetarget portion widths to the optical axis O of the projection system PS.In one embodiment the fluid openings are within two target portionwidths of the optical axis O of the projection system PS.

In the embodiment of FIG. 6 the fluid opening of the substrate surfaceactuator 100 is an opening in the fluid handling structure 12. The fluidopening is arranged to provide fluid therethrough onto the substrate W(as opposed to extraction of fluid from the substrate W). In anembodiment (such as that of FIG. 6) the fluid is liquid. This isdesirable because it is easier to control the force applied by a flow ofliquid than by a flow of gas. Additionally, the magnitude of the forcecan be much greater if the fluid is liquid because of the incompressiblenature of liquid.

The arrangement in FIG. 6 is particularly convenient because the fluidsupplied out of the fluid openings 180 a-c is liquid which is desired tobe present under the fluid openings 180 a-c in any case. That is,because the fluid openings 180 a-c are radially inwardly of the fluidextraction openings 50 in the undersurface of the fluid handlingstructure 12 (which are for the removal of liquid from between the fluidhandling structure 12 and the substrate W) liquid is desired to bepresent under the fluid openings 180 a-c in any case.

In an embodiment the fluid opening of the substrate surface actuator 100is arranged to extract fluid (gas or liquid or both) from between thefluid handling structure and the substrate W. For example, the fluidopening of the substrate surface actuator 100 can be one or more of theextraction openings 50, with the force being varied by varying theunderpressure applied to the opening 50 and thereby the flow ratethrough the opening 50. Alternatively or additionally, as illustratedand described below with reference to FIG. 11, the fluid opening of thesubstrate surface actuator 100 may be an opening of a single phaseextractor (e.g. an extractor for the extraction of liquid in singlephase). Such an extraction system comprises at least one opening whichsurrounds the space 11 between the final element of the projectionsystem PS and the substrate W and resists passage of liquid radiallyoutward relative to the space 11.

As illustrated in FIG. 6 the immersion fluid supply openings 180 a-cforming the fluid opening of the substrate surface actuator 100 may beelongate, for example in the form of a slit. The slit may been dividedinto three discrete fluid openings 180 a, 180 b, 180 c which togethersurround the space 11. There may or may not be gaps between adjacentslits. The gaps may or may not comprise an opening (e.g. an opening 180not being a fluid opening of the substrate surface actuator 100). Therate of flow of fluid through each of the fluid openings 180 a, 180 b,180 c may be controlled individually by the position controller 500. Inan embodiment, the flow through each of the openings 180 a-c iscontrolled by a different controller.

An arrangement with at least three fluid openings surrounding the space11 is advantageous in that the force applied to the substrate W by thesubstrate surface actuator 100 may be varied not only in the Z directionbut also the Rx and Ry directions. The provision of three fluid openings180 a-c avoids over-actuation in that the generation of bending forcesbetween the fluid openings can be avoided.

In an embodiment more than three fluid openings 180 a-c are provided.For example, at least four fluid openings may be provided (as will bedescribed below) and the position controller 500 may vary the fluid flowthrough the at least four openings to generate a bending force on thesubstrate W.

In the embodiment of FIG. 6 the three fluid openings are such that theircenters, in plan, are positioned at substantially 120° intervals aroundthe optical axis O of the projection system PS.

In an embodiment the fluid opening 180 a-c substantially surrounds theoptical axis O of the projection system PS. The fluid opening 180 a-cforms a shape, in plan. In the example of FIG. 6 the shape is that of acircle. However, other shapes are possible, in particular corneredshapes as illustrated in FIGS. 10, 12-16 and 21-23, for example arectilinear shape such as a square, a rhombus or a rectangle optionallywith sides with a negative radius of curvature with respect to thecenter of the shape.

Various arrangements of fluid opening of a circular substrate surfaceactuator 100 are illustrated in FIGS. 17-20.

Instead, or in addition to openings 180 a-c forming the fluid opening ofthe substrate surface actuator 100, the openings 50, or the gas knife210, or both, may form the fluid opening of the substrate surfaceactuator 100. The openings 50 could be divided into more than one groupas illustrated with the openings 180 a-d in FIG. 10. The gas knife 210could be segmented in a similar way to the immersion fluid supplyopenings 180 a-c of FIG. 6. In an embodiment the gas knife 210 may bedefined by a plurality of discrete openings instead of a slit. In anembodiment the openings 50 may be defined by one or more slits insteadof discrete openings.

FIG. 7 illustrates, in cross-section, an embodiment of the fluid opening180 a of a substrate surface actuator 100. The embodiment of FIG. 7illustrates one way in which the fluid flow through the fluid opening180 a may be varied with a suitable frequency. Liquid is provided alonga conduit 300. A mass flow controller 310 controls the flow rate ofliquid through a flow restriction 320 into a chamber 330. The chamber330 is upstream of the fluid opening 180 a. Because of theincompressible nature of liquid, normally the flow rate into the chamber330 is equal to the flow rate of liquid out of the chamber through thefluid opening 180 a. The liquid is directed by the opening 180 a in adirection towards the substrate W. The force between the substratesurface actuator 100 and the substrate W can be varied by changing theflow rate.

One way in which the flow rate can be varied is to provide a plunger340. The plunger 340 is moveable backwards and forwards (in the Xdirection as illustrated) into and out of chamber 330. As the plunger340 moves into chamber 330 more liquid is forced out of the fluidopening 180 a than is usually the case (because the flow restriction 320resists liquid exiting the chamber 330 via the conduit 300). As theplunger 340 retracts out of chamber 330 the flow rate out of fluidopening 180 a is reduced below the normal rate. The rate of extractionof the plunger 340 from the chamber 330 may need to be limited (comparedto the rate of insertion) to avoid cavitation.

In an embodiment, the plunger 340 is driven as a voice coil. The voicecoil is a Lorentz motor comprising coils 342 and permanent magnets inthe plunger 340. A reaction force generated by movement of the plunger340 may be transmitted in the X direction. A reaction force generated inthe X direction can be dealt with without deleteriously affecting thedynamics of the apparatus.

FIG. 8 illustrates an embodiment of how the substrate surface actuator100 is coupled to a reference frame RF of the apparatus. The projectionsystem PS is also to some extent attached to the reference frame RF.Therefore, it is undesirable that forces are transmitted from thesubstrate surface actuator 100 to the reference frame RF where theywould be transmitted onto the projection system PS.

For simplicity in FIG. 8 an embodiment is illustrated in which thesubstrate surface actuator 100 is not part of a fluid handling system toconfine liquid to a space between a final element of the projectionsystem PS and the substrate W. That is, the substrate surface actuator100 of FIG. 8 is in a non immersion lithographic apparatus. However, theprinciples described with reference to FIG. 8 are equally applicablewhere the substrate surface actuator 100 is part of a fluid handlingstructure and in a case where a fluid handling structure is providedseparately to the substrate surface actuator 100.

The forces applied to the substrate through the substrate surfaceactuator 100 are likely to have a frequency in the range of 0 to 500 Hz,perhaps between 0 and 300 Hz, between 1 Hz and 200 Hz, or between 2 Hzand 150 Hz. In order to isolate the reference frame RF from thesevibrations in an embodiment a reaction mass 400 is provided between thesubstrate surface actuator 100 and the reference frame RF. The reactionmass 400 has a relatively high mass (e.g. about 0.5 kg to 5 kg, comparedto a mass of the liquid handling structure 12 or actuator 100 of 2 to 3kg). An actuator 410 is positioned between the reaction mass 400 and thesubstrate surface actuator 100. The actuator 410 is controlled by acontroller (for example the positioning controller 500) in order toposition the substrate surface actuator 100. Thus, the actuator 450positions the substrate surface actuator 100 relative to the referenceframe RF. When a variation in fluid flow through the fluid openingoccurs the substrate surface actuator 100 remains a substantiallyconstant height above the substrate W.

In order to isolate the reaction force from the reference frame RF, anelastic coupling 405 is used to couple the reaction mass 400 to thereference frame RF. The coupling 405 and reaction mass 400 have aneigen-frequency substantially lower than the expected frequency offorces applied to the substrate W by the substrate surface actuator 100.For example, the suspension eigen-frequency is between 2 and 20 Hz,desirably 5 and 15 Hz. A permitted frequency of force variation of thesubstrate surface actuator 100 is 1 kHz or above. Desirably thefrequency is less than 5 kHz. Desirably the permitted frequency of forcevariation of the substrate surface actuator 100 is between 1 and 5 kHz,desirably towards 5 kHz.

In an embodiment the fluid opening may be a fluid opening not used forthe confinement of liquid in the space 11 (and/or provision of liquid tothe immersion space). Examples are illustrated in FIGS. 10, 15, 16, 19and 20 in connection with discrete force applicators 450 describedbelow. The openings may be radially inward or radially outward withrespect to the space 11 of any openings (e.g. 50, 70) in theundersurface of the fluid handling structure 12 used for maintenance ofliquid in the space 11 between the projection system PS and thesubstrate W. The fluid opening of the substrate surface actuator 100 maybe part of a discrete force applicator.

FIG. 9 illustrates in cross-section a discrete force applicator 450comprising a fluid opening 455 of a substrate surface actuator 100 of anembodiment. In the case of FIG. 9 the fluid opening 455 may be anopening of a substrate surface actuator 100 which is not in a fluidhandling structure (such as the embodiment of FIG. 8). Alternatively oradditionally, the fluid opening 455 may be radially outward with respectto a space 11 of any openings in an undersurface of a fluid handlingstructure used for provision and/or maintenance of liquid in a space 11between the projection system and the substrate. Such discrete forceapplicators 450 a, 450 b are illustrated in FIGS. 15, 16, 19 and 20,described below. In this case it is desirable still to have liquid asthe fluid. Therefore, the liquid exiting the fluid opening needs to becollected. For this purpose at least one fluid extraction opening 460 isprovided surrounding the fluid opening 455. The fluid extractionopening(s) 460 is/are connected to an underpressure source to removeliquid on the surface of the substrate W from the fluid opening 455. Inan embodiment, at least three or four of the discrete force applicators450 are used.

FIG. 9 is just an exemplary embodiment and other measures may be takenin order to recover the liquid. Alternatively the fluid exiting thefluid opening 455 may be gas in which case the provision of a fluidextraction opening 460 may not be necessary. The fluid extractionopening 460 surrounds the fluid opening 455. The fluid extractionopening 460 may be in the form of a plurality of openings such as theopenings 50 described above with reference to FIG. 6. In an embodiment,the fluid opening 455 is connected to an underpressure source to applyan attractive force to the substrate W.

Other types of discrete force applicator may be possible.

FIG. 10 illustrates an embodiment which is the same as the embodiment ofFIG. 6 except as described below.

In the FIG. 10 embodiment the openings 50 are positioned so as to form,in plan, a cornered shape (i.e. a shape with corners 52). In the case ofFIG. 10 this is in the shape of a rhombus, desirably a square, withcurved edges or sides 54. The edges 54, if curved, have a negativeradius. The edges 54 may be straight. The edges 54 may curve towards thecenter of the cornered shape in areas away from the corners 52. Anembodiment of the invention may be applied to any shape, in plan,including but not limited to the shape illustrated, for example, arectilinear shape, e.g. a rhombus, a square or rectangle, or a circularshape, a triangular shape, a star shape, an elliptical shape, etc.

The cornered shape has principal axes 110, 120 aligned with the majordirections of travel of the substrate W under the projection system PS.This helps ensure that, below a critical scan speed, the maximum scanspeed is faster than if the openings 50 were arranged in a circularshape. This is because the force on the meniscus between two openings 50is reduced with a factor cos θ. Here θ is the angle of the lineconnecting the two openings 50 relative to the direction in which thesubstrate W is moving.

The use of a square cornered shape allows movement in the step andscanning directions to be at an equal maximum speed. This may beachieved by having each of the corners 52 of the shape aligned with thescanning and stepping directions 110, 120. If movement in one of thedirections, for example the scan direction is preferred to be fasterthan movement in the step direction then a rhombus shape could be used.In such an arrangement the primary axis (e.g. the longest axis) of therhombus may be aligned with the scan direction. For a rhombic shape,although each of the corners may be acute, the angle between twoadjacent sides of the rhombus, for example in the stepping direction,may be obtuse. The obtuse angle may be more than 90° (for exampleselected from the range of about 90° to 120°, in an embodiment selectedfrom the range of about 90° to 105°). In an embodiment selected from therange of about 85° to 105°).

Throughput can be optimized by making the primary axis of the shape ofthe openings 50 aligned with the major direction of travel of thesubstrate (usually the scan direction). A second axis may be alignedwith the other major direction of travel of the substrate (usually thestep direction). It will be appreciated that any arrangement in which θis different to 90° will give an advantage in at least one direction ofmovement. Thus, exact alignment of the principal axes with the majordirections of travel is not vital.

An advantage of providing the edges with a negative radius is that thecorners may be made sharper. An angle selected from the range of 75 to85° or even lower may be achievable for both the corners 52 aligned withthe scan direction and the corners 52 aligned with the step direction.If it were not for this feature then in order for the corners 52 alignedin both directions to have the same angle, those corners would have tohave 90°. If less than 90° were desired it would be necessary to selectone direction to have corners with less than 90° with the result thatthe other corner would have an angle of greater than 90°.

There may be no meniscus pinning feature radially inwardly of theopenings 50. The meniscus is pinned between the openings 50 with dragforces induced by gas flow into the openings 50. A gas drag velocity ofgreater than or equal to about 15 m/s, desirably about 20 m/s should besufficient. The amount of evaporation of liquid from the substrate maybe reduced thereby reducing both splashing of liquid in the form of oneor more droplets as well as thermal expansion/contraction effects.

The gas knife 210 is illustrated as being provided by a series ofdiscrete openings 210. However, in an embodiment the gas knife isprovided as a slit, as in the embodiment of FIG. 6.

In the embodiment of FIG. 10 the fluid openings 180 may be the fluidopenings of the substrate surface actuator 100. As is illustrated, thefluid openings 180 are provided as discrete openings. The discreteopenings may be divided into groups arranged in a line. The fluid flowthrough the openings of a single group may be controlled together by thecontroller 500. As illustrated the fluid openings 180 are divided intofour groups 180 a-d thereby providing the substrate surface actuator 100with four sets of fluid openings. The fluid flow through each set can bevaried to displace and/or orientate and/or bend the substrate W relativeto the projection system under the control of the position controller500. Alternatively or additionally the openings 50 may be the fluidopenings of the substrate surface actuator 100.

Alternatively or additionally discrete force applicators 450 a may beprovided radially inwardly of the openings 50. Alternatively oradditionally discrete force applicators 450 b may be provided radiallyoutwardly of the gas knife openings 210.

The discrete force applicators 450 a, 450 b may be for the provision ofliquid, for example immersion liquid, into the space between theundersurface of the fluid handling structure 12 and the substrate W.

In an embodiment the discrete force applicators 450 b which are providedradially outward of the openings 50 provide gas or liquid onto the topsurface of the substrate W to generate the force. In the case of theopenings 450 b providing liquid, the openings may be as described andillustrated in FIG. 9. Various arrangements of fluid openings of thesubstrate surface actuator 100 are illustrated for a square fluidhandling structure in FIGS. 12-16.

FIG. 11 illustrates a fluid handling structure 12 which is part of aliquid supply system. The fluid handling structure 12 extends around theperiphery (e.g. circumference) of the final element of the projectionsystem PS.

A plurality of openings 20 in the surface which in part defines thespace 11 provides the liquid to the space 11. The liquid passes throughopenings 29, 20 in side walls 28, 22 respectively through respectivechambers 24, 26 prior to entering the space 11.

A seal is provided between the bottom of the fluid handling structure 12and a facing surface, e.g. the substrate W, or a substrate table WT, orboth. In FIG. 11 a seal device is configured to provide a contactlessseal and is made up of several components. Radially outwardly from theoptical axis of the projection system PS, there is provided a (optional)flow control plate 51 which extends into the space 11. The control plate51 may have an opening 55 to permit flow of liquid therethrough; theopening 55 may be beneficial if the control plate 51 is displaced in theZ direction (e.g., parallel to the optical axis of the projection systemPS). Radially outwardly of the flow control plate 51 on the bottomsurface of the fluid handling structure 12 facing (e.g., opposite) thefacing surface, e.g., the substrate W, may be an immersion fluid supplyopening 180. The immersion fluid supply opening 180 can provideimmersion fluid (e.g. liquid, for example an aqueous solution or water)in a direction towards the facing surface. During imaging this may beuseful in preventing bubble formation in the immersion liquid by fillinga gap between the substrate W and substrate table WT with liquid.

Radially outwardly of the immersion fluid supply opening 180 may be anextractor assembly 70 to extract liquid from between the fluid handlingstructure 12 and the facing surface. The extractor assembly 70 mayoperate as a single phase or as a dual phase extractor. The extractorassembly 70 acts as a meniscus pinning feature.

Radially outwardly of the extractor assembly may be a gas knife 210. Anarrangement of the extractor assembly and gas knife is disclosed indetail in United States patent application publication no. US2006/0158627 incorporated herein in its entirety by reference.

The extractor assembly 70 as a single phase extractor may comprise aliquid removal device, extractor or inlet such as the one disclosed inUnited States patent application publication no. US 2006-0038968,incorporated herein in its entirety by reference. In an embodiment, theliquid removal device 70 comprises an inlet which is covered in a porousmaterial 111 which is used to separate liquid from gas to enablesingle-liquid phase liquid extraction. An underpressure in chamber 121is chosen is such that the meniscuses formed in the holes of the porousmaterial 111 substantially prevent ambient gas from being drawn into thechamber 121 of the liquid removal device 70. However, when the surfaceof the porous material 111 comes into contact with liquid there is nomeniscus to restrict flow and the liquid can flow freely into thechamber 121 of the liquid removal device 70.

The porous material 111 has a large number of small holes each with adimension, e.g. a width, such as a diameter, in the range of 5 to 150micrometer, desirably in the range of 5 to 100 micrometers and moredesirably in the range of 5 to 50 micrometers. The porous material 111may be maintained at a height in the range of 50 to 300 micrometersabove a surface, such as a facing surface, from which liquid is to beremoved, e.g. the surface of a substrate W. In an embodiment, porousmaterial 111 is at least slightly liquidphilic, i.e. having a dynamiccontact angle of less than or equal to 90°, desirably less than or equalto 85° or desirably less than or equal to 80°, to the immersion liquid,e.g. water.

In an embodiment, the liquid supply system has an arrangement to dealwith variations in the level of the liquid. This is so that liquid whichbuilds up between the projection system PS and the liquid confinementstructure 12 (forming, e.g., a meniscus 25) can be dealt with and doesnot escape. One way of dealing with this liquid is to provide alyophobic (e.g., hydrophobic) coating. The coating may form a bandaround the top of the fluid handling structure 12 surrounding theopening and/or around the last optical element of the projection systemPS. The coating may be radially outward of the optical axis of theprojection system PS. The lyophobic (e.g., hydrophobic) coating helpskeep the immersion liquid in the space 11. An additional or alternativeway of dealing with this liquid is to provide an outlet 201 to removeliquid reaching a certain point (e.g., height) relative to the liquidconfinement structure 12 and/or projection system PS.

In the fluid handling structure 12 of FIG. 11 the fluid opening of theincorporated substrate surface actuator 100 is illustrated as being theopenings of the extractor 70. That is, by varying the pressure in thechamber 121 using a plunger 340 the force applied by the extractor 70 tothe substrate W may be varied. Alternatively or additionally the liquidsupply opening 180 may be the fluid opening of the substrate surfaceactuator, as described in detail with respect to FIG. 6 or FIG. 10.

In the embodiment of FIG. 11 a gas knife 210 is provided radiallyoutwardly of the extractor 70. In an embodiment the gas knife 210 may bea fluid opening of the substrate surface actuator 100, as with theembodiments of FIGS. 6 and 10. By varying the gas flow out of the gasknife 210 the force applied to the substrate W can be varied.

In an embodiment a fluid opening of the substrate surface actuator 100which is connected to an underpressure source may be provided radiallyoutwardly of the meniscus pinning feature of a fluid handling device(for example the openings 50 of FIGS. 6 and 10 or the extractor 70 ofFIG. 11) and/or radially outwardly of the gas knife 210. Such a fluidopening attached to an underpressure source can be used to apply anattractive force between the substrate surface actuator 100 and thesubstrate W.

The immersion liquid supply opening 180 is particularly suited for useas a substrate surface actuator 100 because during normal use a flow ofliquid onto the substrate W out of the liquid supply opening 180 ispresent. Therefore, an increase or reduction in force between the fluidhandling structure 12/substrate surface actuator 100 and the substrate Wcan be varied in both directions (e.g. increased or decreased).

The control of the substrate surface actuator 100 by the positioncontroller 500 may be feedforward or feedback.

In an embodiment, the position controller 500 adjusts the flow ratethrough the fluid opening of the substrate surface actuator 100 tomaintain a constant total force to the substrate W. This simplifies thecontrol as the second positioner PW need not then be adjusted tocompensate for the total change in force.

One or more sensors may be provided in the substrate surface actuator100. The sensor may be used to measure the position of the substrateand/or a distance between the substrate surface actuator 100 and thesubstrate. The sensor may be of any type including, but not limited tothe group consisting of: a gas (e.g., air) gauge sensor, a capacitorsensor and/or an optical sensor. The sensor may be mounted in/on theundersurface of the body of the actuator 100. A gas knife 210 mayoperate simultaneously as a gas gauge sensor.

The output of the sensor may be provided to the position controller 500.The output may be used to determine a control signal to control the flowrate through the fluid opening of the substrate surface actuator 100and/or to control the actuator 410.

In an embodiment the actuator 410 is not energized when the positioncontroller 500 varies the flow rate of fluid through the fluid openingof the substrate surface actuator 100.

In an embodiment the actuator 410 is driven as a damper by the positioncontroller 500 during variation of fluid flow rate through the fluidopening of the substrate surface actuator 100. When the actuator 410 isdriven as a damper, it is used to help prevent vibrations from reachingthe projection system PS. In an embodiment the actuator 410 isconfigured to lift and lower the substrate surface actuator 100 andconnect it to the reference frame RF.

In order to prevent or reduce cross-talk, a control frequency of thesystem to vary the flow rate (e.g. the voice coil 342) is different fromthat of other components. The restriction 320 between the chamber 330and mass flow controller 310 also helps in this regard. The mass flowcontroller 310 is controlled at low-bandwidth frequencies.

The size of a fluid handling structure 12 determines the size of thesubstrate table WT. This is because the fluid handling structure 12should be supported by the substrate table WT at all positions, forexample while the substrate is scanned. Therefore, by increasing thefootprint of the fluid handling structure 12 the footprint of thesubstrate table WT should be increased. This is undesirable asincreasing the size of the substrate table WT involves larger actuatorsto move the greater mass and a larger footprint of the whole apparatus.Therefore, it is desirable that the fluid opening of the substratesurface actuator 100 does not increase or at least not excessivelyincrease the footprint of the fluid handling structure 12. The use ofdiscrete force applicators 450 within the existing footprint of thefluid handling structure 12 are desirable. If the discrete forceapplicators 450 are outside of the footprint of the existing fluidhandling structure 12 (for example outside of the gas knife 210),locations along the sides in the case of a rectilinear shaped fluidhandling structure (as in FIG. 15) are desired over positioning thediscrete force applicators 450 b at the corners (as in FIG. 16). Thishelps to ensure an outer periphery of the footprint of the discreteforce applicators and the fluid handling structure does not involve alarger, or even excessive, table surface area to support the outerperiphery of the footprint.

FIGS. 12-22 illustrate various arrangements of substrate surfaceactuator. The figures are schematic representations of a selection ofdifferent embodiments of actuator. In the case of the embodiments ofFIGS. 12-14, 17, 18 and 21 to 23 the substrate surface actuator 100 mayor may not be incorporated in a fluid handling structure 12 even thoughthey are labeled as being immersion fluid supply openings 180. In theembodiments of FIGS. 15, 16, 19 and 20 the substrate surface actuator100 is incorporated into a fluid handling structure 12. In thesefigures, the squares or circles represent the shape made, in plan, byfeatures in the undersurface of the fluid handling structure12/substrate surface actuator 100. The lines represent slits (e.g. anelongate opening) or a grouping of a plurality of discrete fluidopenings of the substrate surface actuator 100. In all embodiments theelongate fluid opening or grouping of a plurality of discrete openingsextends around a portion of the shape made in plan.

For the examples of FIGS. 12-14, 17, 18 and 21 to 23 the lines mayrepresent shapes made by a plurality of fluid openings, in plan. Thefluid openings may be fluid openings of a substrate surface actuator 100and/or may be the shape made in plan by openings in the undersurface ofa fluid handling structure 12 (such as openings 50, liquid supplyopenings 180, gas knife 210 etc.).

In the embodiments of FIGS. 12-16 the openings are arranged, in plan, ina cornered shape. In the embodiment of FIGS. 12-16 the shape has fourcorners. The corners 52 are aligned with the scan and step directions ofthe substrate W.

In FIG. 12, the fluid openings are split into three with a leading fluidsupply opening 180 a which incorporates a leading corner 52 a of theshape, in plan. The leading fluid supply opening 180 a extendsequidistantly from the leading corner 52 a. Two other fluid openings 180b, are each provided so as to include a corner which is aligned with thestep direction of the substrate W. The opening 180 b includessubstantially all of one side of the shape, in plan. In an embodiment,the length of the two sorts of opening 180 a, b are the same. In anembodiment, the force applied by the two sorts of opening can be in thesame range.

In the embodiment of FIG. 13 there are four openings 180 a. Each opening180 a extends around a corner of the shape and a portion of the sides ofthe shape. Each opening 180 a may be of the same length. The range offorce applied through each opening may be the same. Each opening 180 amay extend equidistantly from its respective corner.

In the embodiment of FIG. 14 each opening 180 a extends along the lengthof a side and does not incorporate a corner. The length of each opening180 a may be the same. The openings 180 a are positioned substantiallyequidistant from adjacent corners 52.

In the embodiments of FIGS. 15 and 16 discrete force applicators 450such as illustrated in FIG. 9 are provided. Both the embodiments FIGS.15 and 16 illustrate discrete force applicators 450 b outside offeatures used to confine immersion liquid to the space 11 (shown insolid lines). Also shown in dashed lines are discrete force applicators450 a inside features used to maintain liquid in the space 11. Theopenings 450 a, 450 b are the same as those shown in FIG. 10. In theembodiment of FIG. 15 the discrete force applicators 450 a, 450 b areadjacent sides 54 of the shape in plan. The discrete force applicators450 a, 450 b are positioned substantially equidistant from adjacentcorners 52 of the cornered shape.

In the embodiment of FIG. 16 the discrete force applicators 450 a, 450 bare positioned at corners 52 of the shape, in plan. They are positionedadjacent corners 52 of the cornered shape.

In arrangements of the embodiments shown in FIGS. 15 and 16, one or bothof inner and outer discrete force applicators 450 a, 450 b may bepresent.

FIGS. 17 and 18 illustrate a circular arrangement, for example asillustrated in FIG. 6. FIG. 17 illustrates an embodiment where there arethree fluid openings of the substrate surface actuator 100 or threediscrete sets of grouped openings. In an embodiment each of the threeopenings has the same length. In the embodiment of FIG. 17 the center ofeach fluid opening or group is positioned substantially at 120°intervals around an optical axis O of the projection system. FIG. 18illustrates an embodiment in which there are four fluid openings ordiscrete openings grouped into four sets. In the embodiment of FIG. 18the centers, in plan, of the four fluid openings or groups arepositioned at substantially 90° intervals around the optical axis O ofthe projection system.

The embodiments of FIGS. 19 and 20 are the same as the embodiments ofFIGS. 15 and 16 except that the shape made, in plan, is circular ratherthan square. The discrete force applicators 450 a, 450 b may be alignedwith the scanning and stepping directions and the center of the shape,in plan, as shown in FIG. 20. In an embodiment, the discrete forceapplicators 450 a, 450 b are not aligned with the scanning and steppingdirection and the center of the shape in plan, as shown in FIG. 19.

The embodiments of FIGS. 21, 22 and 23 are in the case where the shapemade, in plan, is rectilinear (e.g. rectangular) with the sides alignedwith the scanning and step directions, rather than the corners. Thefluid openings 180 a may be arranged to extend along sides (theembodiment of FIG. 21). The openings 180 a are positioned substantiallyequidistant from adjacent corners 52. The fluid openings 180 b may bearranged to incorporate corners (the embodiment of FIG. 22). Eachopening 180 b may extend equidistantly from its respective corner. Theone or more fluid openings 180 b may incorporate corners and one or morefluid openings 180 a may extend along a side (the embodiment of FIG.23). The embodiments of FIGS. 21-23 may be particularly suited for asystem in which a single phase extractor 70 such as that illustrated inFIG. 11 is used.

In an embodiment, there is provided a lithographic apparatus comprising:a substrate table constructed to hold a substrate; a projection systemconfigured to project a patterned radiation beam onto a target portionof the substrate; a substrate surface actuator comprising a fluidopening for fluid flow therethrough from/onto a facing surface facingthe substrate surface actuator to generate a force between the substratesurface actuator and the facing surface, the facing surface being a topsurface of the substrate or a surface substantially co-planar with thesubstrate; and a position controller to control the position and/ororientation of a part of the facing surface by varying fluid flowthrough the fluid opening to displace the part of the facing surfacerelative to the projection system.

In an embodiment, the position controller is configured to control theposition and/or orientation of a portion of the target portion of thesubstrate. In an embodiment, the substrate surface actuator comprises atleast three fluid openings for fluid flow therethrough to generate aforce between the substrate surface actuator and the facing surface. Inan embodiment, the fluid openings are such that their centers, in plan,are positioned at substantially 120° intervals or lower around anoptical axis of the projection system. In an embodiment, the substratesurface actuator comprises at least four fluid openings for fluid flowtherethrough to generate a force between the substrate surface actuatorand the facing surface. In an embodiment, the position controller isconfigured to control bending of the facing surface by varying fluidflow through the fluid opening(s). In an embodiment, each fluid openingis a group of discrete openings arranged in a line. In an embodiment,the lithographic apparatus further comprises a fluid handling structureconfigured to confine liquid to a space between a final element of theprojection system and the facing surface. In an embodiment, the fluidopening is an opening in the fluid handling structure. In an embodiment,the fluid opening is radially inward with respect to the space of afluid extraction opening formed in an undersurface of the fluid handlingstructure for removal of liquid from between the fluid handlingstructure and the facing surface. In an embodiment, the fluid opening isan opening of an extractor, which surrounds the space between the finalelement of the projection system and the substrate, to resist passage ofliquid radially outward relative to the space. In an embodiment, theextractor is a single phase extractor to extract liquid. In anembodiment, the fluid opening is radially outward with respect to thespace of any openings in an undersurface of the fluid handling structureused for maintenance of liquid in the space between the projectionsystem and the facing surface. In an embodiment, the fluid opening isfor the provision of fluid therethrough onto the facing surface. In anembodiment, the fluid opening is for the provision of liquidtherethrough onto the facing surface. In an embodiment, the fluidopening is for extraction of fluid from the facing surface. In anembodiment, the fluid opening is elongate. In an embodiment, the fluidopening substantially surrounds an optical axis of the projectionsystem. In an embodiment, the fluid opening forms a shape, in plan. Inan embodiment, the lithographic apparatus comprises a plurality of thefluid openings, each fluid opening extending around a portion of theshape. In an embodiment, the shape is a cornered shape. In anembodiment, the shape has at least four corners. In an embodiment, theor at least one fluid opening extends around at least one corner. In anembodiment, the or at least one fluid opening extends between corners.In an embodiment, the or at least one fluid opening is discrete, inplan. In an embodiment, the lithographic apparatus further comprises oneor more other openings to handle fluid on the facing surface, the one ormore other openings arranged in a cornered shape, in plan. In anembodiment, the or each fluid opening is adjacent a corner of thecornered shape. In an embodiment, the or each fluid opening ispositioned substantially equidistant from adjacent corners of thecornered shape. In an embodiment, the lithographic apparatus furthercomprises a chamber upstream of each fluid opening. In an embodiment,the lithographic apparatus further comprises a plunging memberconfigured to insert in and/or extract out of the chamber to vary aforce applied by the substrate surface actuator. In an embodiment, thelithographic apparatus further comprises a mass flow controllerconfigured to provide fluid to the chamber at a certain mass flow rate.In an embodiment, the lithographic apparatus further comprises areference frame to which the projection system and substrate surfaceactuator are coupled. In an embodiment, th lithographic apparatusfurther comprises a reaction mass between the substrate surface actuatorand the reference frame. In an embodiment, the lithographic apparatusfurther comprises an actuator, between the substrate surface actuatorand the reaction mass, to position the substrate surface actuatorrelative to the reference frame. In an embodiment, the reaction mass iscoupled to the reference frame with an eigen frequency of between 1 and50 Hz, between 2 and 20 Hz or between 5 and 15 Hz. In an embodiment, thetarget portion has the target portion width and the fluid openings are,in plan, positioned within a distance of less than 10 target portionwidths of the optical axis of the projection system.

In an embodiment, there is provided a device manufacturing methodcomprising: using a projection system to project a patterned radiationbeam onto a target portion of a substrate; and using a substrate surfaceactuator to control a position and/or orientation of a facing surfacefacing the substrate surface actuator relative to the projection systemby varying fluid flow from/onto the facing surface through a fluidopening of a substrate surface actuator, the facing surface being a topsurface of the substrate or a surface substantially co-planar with thesubstrate.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains one or multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of or about 436, 405, 365, 248, 193, 157 or 126 nm).The term “lens”, where the context allows, may refer to any one orcombination of various types of optical components, including refractiveand reflective optical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention, at least in the form a methodas herein described, may be practiced otherwise than as described. Forexample, the embodiments of the invention, at least in the form of amethod, may take the form of a computer program containing one or moresequences of machine-readable instructions describing a method asdisclosed above, or a data storage medium (e.g. semiconductor memory,magnetic or optical disk) having such a computer program stored therein.Further, the machine readable instruction may be embodied in two or morecomputer programs. The two or more computer programs may be stored onone or more different memories and/or data storage media.

Any controllers described herein may each or in combination be operablewhen the one or more computer programs are read by one or more computerprocessors located within at least one component of the lithographicapparatus. The controllers may each or in combination have any suitableconfiguration for receiving, processing, and sending signals. One ormultiple processors are configured to communicate with at least one ofthe controllers. For example, each controller may include one or moreprocessors for executing the computer programs that includemachinereadable instructions for the methods described above. Thecontrollers may include data storage media for storing such computerprograms, and/or hardware to receive such media. So the controller(s)may operate according the machine readable instructions of one or morecomputer programs.

The invention may be applied to substrates with a diameter of 300 mm or450 mm or any other size.

One or more embodiments of the invention may be applied to any immersionlithography apparatus, in particular, but not exclusively, those typesmentioned above and whether the immersion liquid is provided in the formof a bath, only on a localized surface area of the substrate, or isunconfined. In an unconfined arrangement, the immersion liquid may flowover the surface of the substrate and/or substrate table so thatsubstantially the entire uncovered surface of the substrate table and/orsubstrate is wetted. In such an unconfined immersion system, the liquidsupply system may not confine the immersion liquid or it may provide aproportion of immersion liquid confinement, but not substantiallycomplete confinement of the immersion liquid.

A liquid supply system as contemplated herein should be broadlyconstrued. In certain embodiments, it may be a mechanism or combinationof structures that provides a liquid to a space between the projectionsystem and the substrate and/or substrate table. It may comprise acombination of one or more structures, one or more fluid openingsincluding one or more liquid openings, one or more gas openings or oneor more openings for two phase flow. The openings may each be an inletinto the immersion space (or an outlet from a fluid handling structure)or an outlet out of the immersion space (or an inlet into the fluidhandling structure). In an embodiment, a surface of the space may be aportion of the substrate and/or substrate table, or a surface of thespace may completely cover a surface of the substrate and/or substratetable, or the space may envelop the substrate and/or substrate table.The liquid supply system may optionally further include one or moreelements to control the position, quantity, quality, shape, flow rate orany other features of the liquid.

In an embodiment, the lithographic apparatus is a multi-stage apparatuscomprising two or more tables located at the exposure side of theprojection system, each table comprising and/or holding one or moreobjects. In an embodiment, one or more of the tables may hold aradiation-sensitive substrate. In an embodiment, one or more of thetables may hold a sensor to measure radiation from the projectionsystem. In an embodiment, the multi-stage apparatus comprises a firsttable configured to hold a radiation-sensitive substrate (i.e., asubstrate table) and a second table not configured to hold aradiation-sensitive substrate (referred to hereinafter generally, andwithout limitation, as a measurement and/or cleaning table). The secondtable may comprise and/or may hold one or more objects, other than aradiation-sensitive substrate. Such one or more objects may include oneor more selected from the following: a sensor to measure radiation fromthe projection system, one or more alignment marks, and/or a cleaningdevice (to clean, e.g., the liquid confinement structure).

In an embodiment, the lithographic apparatus may comprise an encodersystem to measure the position, velocity, etc. of a component of theapparatus. In an embodiment, the component comprises a substrate table.In an embodiment, the component comprises a measurement and/or cleaningtable. The encoder system may be in addition to or an alternative to theinterferometer system described herein for the tables. The encodersystem comprises a sensor, transducer or readhead associated, e.g.,paired, with a scale or grid. In an embodiment, the movable component(e.g., the substrate table and/or the measurement and/or cleaning table)has one or more scales or grids and a frame of the lithographicapparatus with respect to which the component moves has one or more ofsensors, transducers or readheads. The one or more of sensors,transducers or readheads cooperate with the scale(s) or grid(s) todetermine the position, velocity, etc. of the component. In anembodiment, a frame of the lithographic apparatus with respect to whicha component moves has one or more scales or grids and the movablecomponent (e.g., the substrate table and/or the measurement and/orcleaning table) has one or more of sensors, transducers or readheadsthat cooperate with the scale(s) or grid(s) to determine the position,velocity, etc. of the component.

In an embodiment, the lithographic apparatus comprises a liquidconfinement structure that has a liquid removal device (or meniscuspinning feature) having an inlet covered with a mesh or similar porousmaterial. The mesh or similar porous material provides a two-dimensionalarray of holes contacting the immersion liquid in a space between thefinal element of the projection system and a movable table (e.g., thesubstrate table). In an embodiment, the mesh or similar porous materialcomprises a honeycomb or other polygonal mesh. In an embodiment, themesh or similar porous material comprises a metal mesh. In anembodiment, the mesh or similar porous material extends all the wayaround the image field of the projection system of the lithographicapparatus. In an embodiment, the mesh or similar porous material islocated on a bottom surface of the liquid confinement structure and hasa surface facing towards the table. In an embodiment, the mesh orsimilar porous material has at least a portion of its bottom surfacegenerally parallel with a top surface of the table.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

The invention claimed is:
 1. A lithographic apparatus comprising: amovable table; a projection system configured to project a radiationbeam onto a radiation-sensitive portion of a substrate; a first fluidhandling structure configured to at least partly confine liquid to animmersion space between the projection system and a facing surface, thefacing surface being a top surface of the substrate or table; a secondfluid handling structure configured to supply liquid to a separate spacebetween the second fluid handling structure and the facing surface, theseparate space spaced horizontally from the immersion space; a thirdfluid handling structure comprising a fluid port opening to a regionbetween the third fluid handling structure and the facing surface, theregion spaced horizontally inward, relative to a center of the immersionspace, of the separate space and the fluid port opening configured toprovide fluid to the region; and an actuator configured to displace thethird fluid handling structure relative to the first and second fluidhandling structures.
 2. The apparatus of claim 1, wherein the secondfluid handling structure further comprises a sensor configured todetermine a distance to the facing surface.
 3. The apparatus of claim 1,wherein the second fluid handling structure comprises an inletconfigured to supply the liquid and an outlet configured to removeliquid, the outlet surrounding the inlet.
 4. The apparatus of claim 3,wherein the outlet is circular in shape in the horizontal.
 5. Theapparatus of claim 1, wherein the first fluid handling structure has anoutlet configured to remove liquid arranged in a cornered shape around apath of the radiation through the space, and comprising a plurality ofsecond fluid handling structures, each second fluid handling structurelocated at a corner of the cornered shape.
 6. The apparatus of claim 1,further comprising a balance mass configured to absorb a reaction forceassociated with displacement of the second fluid handling structure. 7.The apparatus of claim 1, wherein the second fluid handling structure islocated away from an outer periphery of the first fluid handlingstructure.
 8. The apparatus of claim 1, further comprising an actuatorconfigured to displace the second fluid handling structure relative tothe first fluid handling structure with a directional component in thevertical.
 9. A lithographic apparatus comprising: a movable table; aprojection system configured to project a patterned radiation beam ontoa target portion of a substrate; a first fluid handling structureconfigured to at least partly confine liquid to an immersion spacebetween the projection system and a facing surface, the facing surfacebeing a top surface of the substrate or table; a second fluid handlingstructure configured to supply liquid to a space between the secondfluid handling structure and the facing surface, the second fluidhandling structure separated by a horizontal gap from an outer peripheryof the first fluid handling structure; a third fluid handling structurecomprising a fluid port opening to a region between the third fluidhandling structure and the facing surface, the region spacedhorizontally inward, relative to a center of the immersion space, of theseparate space and the fluid port opening configured to provide fluid tothe region; and an actuator configured to displace the third fluidhandling structure relative to the first and second fluid handlingstructures.
 10. The apparatus of claim 9, wherein the second fluidhandling structure further comprises a sensor configured to determine adistance to the facing surface.
 11. The apparatus of claim 9, whereinthe second fluid handling structure comprises an inlet configured tosupply the liquid and an outlet configured to remove liquid, the outletsurrounding the inlet.
 12. The apparatus of claim 11, wherein the outletis circular in shape in the horizontal.
 13. The apparatus of claim 9,wherein the first fluid handling structure has an outlet configured toremove liquid arranged in a cornered shape around a path of theradiation through the space, and comprising a plurality of second fluidhandling structures, each second fluid handling structure located at acorner of the cornered shape.
 14. The apparatus of claim 9, furthercomprising a balance mass configured to absorb a reaction forceassociated with displacement of the second fluid handling structure. 15.The apparatus of claim 9, further comprising an actuator configured todisplace the second fluid handling structure relative to the first fluidhandling structure with a directional component in the vertical.
 16. Adevice manufacturing method comprising: using a projection system toproject a radiation beam, through a liquid in an immersion space, onto aradiation-sensitive portion of a substrate; at least partly confiningthe liquid to the immersion space between the projection system and afacing surface using a first fluid handling structure, the facingsurface being a top surface of the substrate or a movable table;supplying and confining liquid to a separate space between a secondfluid handling structure and the facing surface using a second fluidhandling structure, the separate space spaced horizontally from theimmersion space and the second fluid handling structure located outsidea periphery of the first fluid handling structure; supplying a fluid,using a fluid port opening of a third fluid handling structure, to aregion between the third fluid handling structure and the facingsurface, the region spaced horizontally inward, relative to a center ofthe immersion space, of the separate space; and displacing the thirdfluid handling structure relative to the first and second fluid handlingstructures.
 17. The method of claim 16, further comprising determining adistance to the facing surface using a sensor of the second fluidhandling structure.
 18. The method of claim 16, further comprisingsupplying liquid using an inlet of the second fluid handling structureand removing liquid using an outlet of the second fluid handlingstructure surrounding the inlet, wherein the outlet is circular in shapein the horizontal.
 19. The method of claim 16, wherein the first fluidhandling structure has an outlet configured to remove liquid arranged ina cornered shape around a path of the radiation through the space, andcomprising confining liquid to a plurality of separate spaces using aplurality of second fluid handling structures, each second fluidhandling structure located at a corner of the cornered shape.
 20. Themethod of claim 16, further comprising displacing the second fluidhandling structure relative to the first fluid handling structure with adirectional component in the vertical using an actuator.